A student in my Fetal Monitoring for Maternity Professionals course asked me about this recently – and I realised I had never written about it, despite having promised to do so a few times! This is for Natalie, with gratitude.
What is the Dawes Redman system?
As an Australia maternity care provider, I have never encountered the Dawes Redman system in clinical practice. Its use seems to be widespread in the United Kingdom, where it originated. So if you haven’t heard of it before – it’s probably simply a matter of geography!
The system is named after Geoffrey Dawes and Christopher Redman, both from an Oxford based team of researchers with a long history of research and development relating to fetal monitoring. In 1991, they brought a CTG system into commercial production known as the System 8000. Years of development had gone into refining the capture of heart rate information from a Doppler sensor and processing of that signal to ensure a high level of accuracy.
The heart rate pattern is analysed according to a predetermined algorithm to determine whether the pattern is “normal” or not. (You can find the details of the specific criteria the system uses in Jones et al., 2022). The Dawes Redman system is therefore a form of computerised analysis of the CTG using artificial intelligence, designed specifically and exclusively for use in the antenatal period.
Does it work?
Initial research confirmed a link between heart rate patterns considered abnormal by the computer criteria and high levels of acid in the umbilical cord blood, either during pregnancy or at birth (Guzman, et al., 1996; Ribbert et al., 1991). This research was done only in fetuses considered small for gestational age, so the findings may not apply to other fetuses. While there is a link between cord blood acidosis and perinatal mortality or brain injury, the link isn’t particularly strong (Johnson et al., 2021) – so this on its own isn’t compelling evidence to support the use of the system.
Better evidence comes from the two randomised controlled trials that have been done, and are summarised in the Grivell et al., 2015 Cochrane review about antenatal CTG use. The trials were done in 1997 and 1999, and recruited 469 women considered to be a high risk. They compared the Dawes Redman computer analysis approach with standard antenatal (non-stress test) CTG monitoring. Before we dig into these – let’s remind ourselves that the purpose of antenatal CTG monitoring is to prevent stillbirth, or the birth a baby who dies soon after birth, or develops irreversible brain injury.
How was the research done?
One trial was in Africa – and all the women recruited were preterm and had preeclampsia (Steyn & Odendaal, 1997). The other trial was in New York (Bracero, Morgan, & Byrne, 1999). They also recruited “high risk” women, with a broad range of inclusion criteria. “Postdates” was the most common, and reduced movements, diabetes, hypertension, and growth restriction were also included among others. The New York study used ultrasound with biophysical profile scores in addition to CTG monitoring. The African study didn’t specifically say ultrasound was used, but there is mention of an elective caesarean section at 29 weeks for absent end diastolic flow (something that can only be done by ultrasound), so at least some women also had ultrasound monitoring.
When I looked at the details in the papers, all the deaths in the African study read as complications of prematurity to me (they included necrotising enterocolitis, sepsis, and pulmonary haemorrhage), rather than being due to low oxygen levels. The deaths in the New York study included one stillbirth at 38 weeks that happened 4 days after a standard (and reactive) CTG done for a woman with diabetes, and all the other deaths were infants who had congenital abnormalities.
When both trials are combined, there was a significant reduction in perinatal mortality with the computerised system (from 4.2% to 0.9%), but when they excluded the infants with major congenital anomalies the difference was no longer significant. There was no difference in the caesarean section rate, Apgar scores, length of stay in neonatal intensive care, or gestational age at birth. They did no long term follow up, so whether it made a difference to brain injury rates, we don’t know.
So what does this mean?
Computer interpretation with the Dawes Redman system might be a bit better than standard antenatal CTG use – but the evidence comes from a small number of women, and is a bit old now. I’d love to see several big trials, with suitably long follow up, and to have a number of “single” risk trials to know if it works for specific populations of women. Only one of the deaths was the kind of thing we imagine that antenatal CTG use might be able to prevent. There is no research comparing the Dawes Redman system with not using a CTG, so we don’t know if it is better than using intermittent auscultation or some other approach to antenatal fetal monitoring.
What I find most fascinating about the Dawes Redman system is that its use seems to remain confined to the United Kingdom (let me know in the comments if you are using it somewhere else in the world). We have seen the introduction of other forms of fetal monitoring technology on a widespread basis in high income countries where there is far less evidence and not even a hint that it might work (I’m looking at you, central fetal monitoring…). I don’t know the answer as to why this particular system hasn’t captured people’s imagination!
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References
Bracero, L. A., Morgan, S., & Byrne, D. W. (1999, Nov). Comparison of visual and computerized interpretation of nonstress test results in a randomized controlled trial. American Journal of Obstetrics and Gynecology, 181(5 Pt 1), 1254-1258. https://doi.org/10.1016/s0002-9378(99)70118-3
Grivell, R. M., Alfirevic, Z., Gyte, G. M., & Devane, D. (2015, Sep 12). Antenatal cardiotocography for fetal assessment. Cochrane Database of Systematic Review, 2015(9), CD007863. https://doi.org/10.1002/14651858.CD007863.pub4
Guzman, E., Vintzileos, A., Martins, M., Benito, C., Houlihan, C., & Hanley, M. (1996). The efficacy of individual computer heart rate indices in detecting academia at birth in growth-restricted fetuses. Obstetrics & Gynecology, 87(6), 969-974. https://doi.org/10.1016/0029-7844(96)00020-8
Johnson, G. J., Salmanian, B., Denning, S. G., Belfort, M. A., Sundgren, N. C., & Clark, S. L. (2021, Sep 1). Relationship between umbilical cord gas values and neonatal outcomes: Implications for electronic fetal heart rate monitoring. Obstetrics & Gynecology, 138(3), 366-373. https://doi.org/10.1097/AOG.0000000000004515
Jones, G.D., Cooke, W. R., Vatish, M., & Redman, C.W.G. (2022). Computerized analysis of antepartum cardiotocography: A review. Maternal-Fetal Medicine, 4(2), 130-140. DOI: 10.1097/FM9.0000000000000141
Ribbert, L.S., Snijders, R.J., Nicolaides, K.H. et al. (1991). Relation of fetal blood gases and data from computer-assisted analysis of fetal heart rate patterns in small for gestation fetuses. British Journal of Obstetrics & Gynaecol0gy, 98(8), 820–823. doi:10.1111/j.1471-0528.1991.tb13489.x.
Steyn, D. W., & Odendaal, H. J. (1997, Jan 05). Routine or computerized cardiotocography in severe preeclampsia? A randomized controlled tiral. Journal of Maternal Fetal Investigation, 7, 166-171. https://scholar.sun.ac.za/items/75715e18-3933-4da7-862b-8489e20c3c0b
Categories: antenatal CTG, CTG, EFM, Perinatal brain injury, Perinatal mortality
Tags: Artificial intelligence, computerised interpretation, Dawes Redman
Birth Small Talk 
I’m a UK midwife, working in Australia for the last year. I hate Dawes Redman with a passion, and have very little trust in it. I worked in a very busy antenatal triage in England, so lots of reduced FMs, APH, pre-IOL CTG etc so used it a lot. It would make random decisions like it’s criteria would be met with a huge decel (not in labour), or it would meet criteria after 10 minutes when a baseline wasn’t determinable. My clinical judgement overruled decisions like that, but I worry once it becomes more mainstream it will give false reassurance and deskill midwives in being able to interpret CTG.
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